DESCRIPTION

Incorporates changes from the named commits (since the time their
histories diverged from the current branch) into the current
branch. This command is used by git pull to incorporate changes
from another repository and can be used by hand to merge changes
from one branch into another.

Assume the following history exists and the current branch is
"master":

A---B---C topic
/
D---E---F---G master

Then "git merge topic" will replay the changes made on the
topic branch since it diverged from master (i.e., E) until
its current commit (C) on top of master, and record the result
in a new commit along with the names of the two parent commits and
a log message from the user describing the changes.

A---B---C topic
/ \
D---E---F---G---H master

The second syntax (<msg> HEAD <commit>…) is supported for
historical reasons. Do not use it from the command line or in
new scripts. It is the same as git merge -m <msg> <commit>....

The third syntax ("git merge --abort") can only be run after the
merge has resulted in conflicts. git merge --abort will abort the
merge process and try to reconstruct the pre-merge state. However,
if there were uncommitted changes when the merge started (and
especially if those changes were further modified after the merge
was started), git merge --abort will in some cases be unable to
reconstruct the original (pre-merge) changes. Therefore:

Warning: Running git merge with non-trivial uncommitted changes is
discouraged: while possible, it may leave you in a state that is hard to
back out of in the case of a conflict.

OPTIONS

--commit

--no-commit

Perform the merge and commit the result. This option can
be used to override --no-commit.

With --no-commit perform the merge but pretend the merge
failed and do not autocommit, to give the user a chance to
inspect and further tweak the merge result before committing.

--edit

-e

--no-edit

Invoke an editor before committing successful mechanical merge to
further edit the auto-generated merge message, so that the user
can explain and justify the merge. The --no-edit option can be
used to accept the auto-generated message (this is generally
discouraged).
The --edit (or -e) option is still useful if you are
giving a draft message with the -m option from the command line
and want to edit it in the editor.

Older scripts may depend on the historical behaviour of not allowing the
user to edit the merge log message. They will see an editor opened when
they run git merge. To make it easier to adjust such scripts to the
updated behaviour, the environment variable GIT_MERGE_AUTOEDIT can be
set to no at the beginning of them.

--ff

When the merge resolves as a fast-forward, only update the branch
pointer, without creating a merge commit. This is the default
behavior.

--no-ff

Create a merge commit even when the merge resolves as a
fast-forward. This is the default behaviour when merging an
annotated (and possibly signed) tag.

--ff-only

Refuse to merge and exit with a non-zero status unless the
current HEAD is already up-to-date or the merge can be
resolved as a fast-forward.

--log[=<n>]

--no-log

In addition to branch names, populate the log message with
one-line descriptions from at most <n> actual commits that are being
merged. See also git-fmt-merge-msg[1].

With --no-log do not list one-line descriptions from the
actual commits being merged.

--stat

-n

--no-stat

Show a diffstat at the end of the merge. The diffstat is also
controlled by the configuration option merge.stat.

With -n or --no-stat do not show a diffstat at the end of the
merge.

--squash

--no-squash

Produce the working tree and index state as if a real merge
happened (except for the merge information), but do not actually
make a commit, move the HEAD, or record $GIT_DIR/MERGE_HEAD
(to cause the next git commit command to create a merge
commit). This allows you to create a single commit on top of
the current branch whose effect is the same as merging another
branch (or more in case of an octopus).

With --no-squash perform the merge and commit the result. This
option can be used to override --squash.

-s <strategy>

--strategy=<strategy>

Use the given merge strategy; can be supplied more than
once to specify them in the order they should be tried.
If there is no -s option, a built-in list of strategies
is used instead (git merge-recursive when merging a single
head, git merge-octopus otherwise).

-X <option>

--strategy-option=<option>

Pass merge strategy specific option through to the merge
strategy.

--verify-signatures

--no-verify-signatures

Verify that the commits being merged have good and trusted GPG signatures
and abort the merge in case they do not.

--summary

--no-summary

Synonyms to --stat and --no-stat; these are deprecated and will be
removed in the future.

-q

--quiet

Operate quietly. Implies --no-progress.

-v

--verbose

Be verbose.

--progress

--no-progress

Turn progress on/off explicitly. If neither is specified,
progress is shown if standard error is connected to a terminal.
Note that not all merge strategies may support progress
reporting.

-S[<keyid>]

--gpg-sign[=<keyid>]

GPG-sign the resulting merge commit.

-m <msg>

Set the commit message to be used for the merge commit (in
case one is created).

If --log is specified, a shortlog of the commits being merged
will be appended to the specified message.

The git fmt-merge-msg command can be
used to give a good default for automated git merge
invocations.

--[no-]rerere-autoupdate

Allow the rerere mechanism to update the index with the
result of auto-conflict resolution if possible.

--abort

Abort the current conflict resolution process, and
try to reconstruct the pre-merge state.

If there were uncommitted worktree changes present when the merge
started, git merge --abort will in some cases be unable to
reconstruct these changes. It is therefore recommended to always
commit or stash your changes before running git merge.

git merge --abort is equivalent to git reset --merge when
MERGE_HEAD is present.

<commit>…

Commits, usually other branch heads, to merge into our branch.
Specifying more than one commit will create a merge with
more than two parents (affectionately called an Octopus merge).

If no commit is given from the command line, merge the remote-tracking
branches that the current branch is configured to use as its upstream.
See also the configuration section of this manual page.

PRE-MERGE CHECKS

Before applying outside changes, you should get your own work in
good shape and committed locally, so it will not be clobbered if
there are conflicts. See also git-stash[1].
git pull and git merge will stop without doing anything when
local uncommitted changes overlap with files that git pull/git
merge may need to update.

To avoid recording unrelated changes in the merge commit,
git pull and git merge will also abort if there are any changes
registered in the index relative to the HEAD commit. (One
exception is when the changed index entries are in the state that
would result from the merge already.)

If all named commits are already ancestors of HEAD, git merge
will exit early with the message "Already up-to-date."

FAST-FORWARD MERGE

Often the current branch head is an ancestor of the named commit.
This is the most common case especially when invoked from git
pull: you are tracking an upstream repository, you have committed
no local changes, and now you want to update to a newer upstream
revision. In this case, a new commit is not needed to store the
combined history; instead, the HEAD (along with the index) is
updated to point at the named commit, without creating an extra
merge commit.

This behavior can be suppressed with the --no-ff option.

TRUE MERGE

Except in a fast-forward merge (see above), the branches to be
merged must be tied together by a merge commit that has both of them
as its parents.

A merged version reconciling the changes from all branches to be
merged is committed, and your HEAD, index, and working tree are
updated to it. It is possible to have modifications in the working
tree as long as they do not overlap; the update will preserve them.

When it is not obvious how to reconcile the changes, the following
happens:

The HEAD pointer stays the same.

The MERGE_HEAD ref is set to point to the other branch head.

Paths that merged cleanly are updated both in the index file and
in your working tree.

For conflicting paths, the index file records up to three
versions: stage 1 stores the version from the common ancestor,
stage 2 from HEAD, and stage 3 from MERGE_HEAD (you
can inspect the stages with git ls-files -u). The working
tree files contain the result of the "merge" program; i.e. 3-way
merge results with familiar conflict markers <<<===>>>.

No other changes are made. In particular, the local
modifications you had before you started merge will stay the
same and the index entries for them stay as they were,
i.e. matching HEAD.

If you tried a merge which resulted in complex conflicts and
want to start over, you can recover with git merge --abort.

MERGING TAG

When merging an annotated (and possibly signed) tag, Git always
creates a merge commit even if a fast-forward merge is possible, and
the commit message template is prepared with the tag message.
Additionally, if the tag is signed, the signature check is reported
as a comment in the message template. See also git-tag[1].

When you want to just integrate with the work leading to the commit
that happens to be tagged, e.g. synchronizing with an upstream
release point, you may not want to make an unnecessary merge commit.

In such a case, you can "unwrap" the tag yourself before feeding it
to git merge, or pass --ff-only when you do not have any work on
your own. e.g.

git fetch origin
git merge v1.2.3^0
git merge --ff-only v1.2.3

HOW CONFLICTS ARE PRESENTED

During a merge, the working tree files are updated to reflect the result
of the merge. Among the changes made to the common ancestor’s version,
non-overlapping ones (that is, you changed an area of the file while the
other side left that area intact, or vice versa) are incorporated in the
final result verbatim. When both sides made changes to the same area,
however, Git cannot randomly pick one side over the other, and asks you to
resolve it by leaving what both sides did to that area.

By default, Git uses the same style as the one used by the "merge" program
from the RCS suite to present such a conflicted hunk, like this:

Here are lines that are either unchanged from the common
ancestor, or cleanly resolved because only one side changed.
<<<<<<< yours:sample.txt
Conflict resolution is hard;
let's go shopping.
=======
Git makes conflict resolution easy.
>>>>>>> theirs:sample.txt
And here is another line that is cleanly resolved or unmodified.

The area where a pair of conflicting changes happened is marked with markers
<<<<<<<, =======, and >>>>>>>. The part before the =======
is typically your side, and the part afterwards is typically their side.

The default format does not show what the original said in the conflicting
area. You cannot tell how many lines are deleted and replaced with
Barbie’s remark on your side. The only thing you can tell is that your
side wants to say it is hard and you’d prefer to go shopping, while the
other side wants to claim it is easy.

An alternative style can be used by setting the "merge.conflictstyle"
configuration variable to "diff3". In "diff3" style, the above conflict
may look like this:

Here are lines that are either unchanged from the common
ancestor, or cleanly resolved because only one side changed.
<<<<<<< yours:sample.txt
Conflict resolution is hard;
let's go shopping.
|||||||
Conflict resolution is hard.
=======
Git makes conflict resolution easy.
>>>>>>> theirs:sample.txt
And here is another line that is cleanly resolved or unmodified.

In addition to the <<<<<<<, =======, and >>>>>>> markers, it uses
another ||||||| marker that is followed by the original text. You can
tell that the original just stated a fact, and your side simply gave in to
that statement and gave up, while the other side tried to have a more
positive attitude. You can sometimes come up with a better resolution by
viewing the original.

HOW TO RESOLVE CONFLICTS

After seeing a conflict, you can do two things:

Decide not to merge. The only clean-ups you need are to reset
the index file to the HEAD commit to reverse 2. and to clean
up working tree changes made by 2. and 3.; git merge --abort
can be used for this.

Resolve the conflicts. Git will mark the conflicts in
the working tree. Edit the files into shape and
git add them to the index. Use git commit to seal the deal.

You can work through the conflict with a number of tools:

Use a mergetool. git mergetool to launch a graphical
mergetool which will work you through the merge.

Look at the diffs. git diff will show a three-way diff,
highlighting changes from both the HEAD and MERGE_HEAD
versions.

Look at the diffs from each branch. git log --merge -p <path>
will show diffs first for the HEAD version and then the
MERGE_HEAD version.

Look at the originals. git show :1:filename shows the
common ancestor, git show :2:filename shows the HEAD
version, and git show :3:filename shows the MERGE_HEAD
version.

EXAMPLES

Merge branches fixes and enhancements on top of
the current branch, making an octopus merge:

$ git merge fixes enhancements

Merge branch obsolete into the current branch, using ours
merge strategy:

$ git merge -s ours obsolete

Merge branch maint into the current branch, but do not make
a new commit automatically:

$ git merge --no-commit maint

This can be used when you want to include further changes to the
merge, or want to write your own merge commit message.

You should refrain from abusing this option to sneak substantial
changes into a merge commit. Small fixups like bumping
release/version name would be acceptable.

MERGE STRATEGIES

The merge mechanism (git merge and git pull commands) allows the
backend merge strategies to be chosen with -s option. Some strategies
can also take their own options, which can be passed by giving -X<option>
arguments to git merge and/or git pull.

resolve

This can only resolve two heads (i.e. the current branch
and another branch you pulled from) using a 3-way merge
algorithm. It tries to carefully detect criss-cross
merge ambiguities and is considered generally safe and
fast.

recursive

This can only resolve two heads using a 3-way merge
algorithm. When there is more than one common
ancestor that can be used for 3-way merge, it creates a
merged tree of the common ancestors and uses that as
the reference tree for the 3-way merge. This has been
reported to result in fewer merge conflicts without
causing mismerges by tests done on actual merge commits
taken from Linux 2.6 kernel development history.
Additionally this can detect and handle merges involving
renames. This is the default merge strategy when
pulling or merging one branch.

The recursive strategy can take the following options:

ours

This option forces conflicting hunks to be auto-resolved cleanly by
favoring our version. Changes from the other tree that do not
conflict with our side are reflected to the merge result.
For a binary file, the entire contents are taken from our side.

This should not be confused with the ours merge strategy, which does not
even look at what the other tree contains at all. It discards everything
the other tree did, declaring our history contains all that happened in it.

theirs

This is the opposite of ours.

patience

With this option, merge-recursive spends a little extra time
to avoid mismerges that sometimes occur due to unimportant
matching lines (e.g., braces from distinct functions). Use
this when the branches to be merged have diverged wildly.
See also git-diff[1]--patience.

diff-algorithm=[patience|minimal|histogram|myers]

Tells merge-recursive to use a different diff algorithm, which
can help avoid mismerges that occur due to unimportant matching
lines (such as braces from distinct functions). See also
git-diff[1]--diff-algorithm.

ignore-space-change

ignore-all-space

ignore-space-at-eol

Treats lines with the indicated type of whitespace change as
unchanged for the sake of a three-way merge. Whitespace
changes mixed with other changes to a line are not ignored.
See also git-diff[1]-b, -w, and
--ignore-space-at-eol.

If their version only introduces whitespace changes to a line,
our version is used;

If our version introduces whitespace changes but their
version includes a substantial change, their version is used;

Otherwise, the merge proceeds in the usual way.

renormalize

This runs a virtual check-out and check-in of all three stages
of a file when resolving a three-way merge. This option is
meant to be used when merging branches with different clean
filters or end-of-line normalization rules. See "Merging
branches with differing checkin/checkout attributes" in
gitattributes[5] for details.

no-renormalize

Disables the renormalize option. This overrides the
merge.renormalize configuration variable.

rename-threshold=<n>

Controls the similarity threshold used for rename detection.
See also git-diff[1]-M.

subtree[=<path>]

This option is a more advanced form of subtree strategy, where
the strategy makes a guess on how two trees must be shifted to
match with each other when merging. Instead, the specified path
is prefixed (or stripped from the beginning) to make the shape of
two trees to match.

octopus

This resolves cases with more than two heads, but refuses to do
a complex merge that needs manual resolution. It is
primarily meant to be used for bundling topic branch
heads together. This is the default merge strategy when
pulling or merging more than one branch.

ours

This resolves any number of heads, but the resulting tree of the
merge is always that of the current branch head, effectively
ignoring all changes from all other branches. It is meant to
be used to supersede old development history of side
branches. Note that this is different from the -Xours option to
the recursive merge strategy.

subtree

This is a modified recursive strategy. When merging trees A and
B, if B corresponds to a subtree of A, B is first adjusted to
match the tree structure of A, instead of reading the trees at
the same level. This adjustment is also done to the common
ancestor tree.

With the strategies that use 3-way merge (including the default, recursive),
if a change is made on both branches, but later reverted on one of the
branches, that change will be present in the merged result; some people find
this behavior confusing. It occurs because only the heads and the merge base
are considered when performing a merge, not the individual commits. The merge
algorithm therefore considers the reverted change as no change at all, and
substitutes the changed version instead.

CONFIGURATION

merge.conflictstyle

Specify the style in which conflicted hunks are written out to
working tree files upon merge. The default is "merge", which
shows a <<<<<<< conflict marker, changes made by one side,
a ======= marker, changes made by the other side, and then
a >>>>>>> marker. An alternate style, "diff3", adds a |||||||
marker and the original text before the ======= marker.

merge.defaultToUpstream

If merge is called without any commit argument, merge the upstream
branches configured for the current branch by using their last
observed values stored in their remote-tracking branches.
The values of the branch.<current branch>.merge that name the
branches at the remote named by branch.<current branch>.remote
are consulted, and then they are mapped via remote.<remote>.fetch
to their corresponding remote-tracking branches, and the tips of
these tracking branches are merged.

merge.ff

By default, Git does not create an extra merge commit when merging
a commit that is a descendant of the current commit. Instead, the
tip of the current branch is fast-forwarded. When set to false,
this variable tells Git to create an extra merge commit in such
a case (equivalent to giving the --no-ff option from the command
line). When set to only, only such fast-forward merges are
allowed (equivalent to giving the --ff-only option from the
command line).

merge.log

In addition to branch names, populate the log message with at
most the specified number of one-line descriptions from the
actual commits that are being merged. Defaults to false, and
true is a synonym for 20.

merge.renameLimit

The number of files to consider when performing rename detection
during a merge; if not specified, defaults to the value of
diff.renameLimit.

merge.renormalize

Tell Git that canonical representation of files in the
repository has changed over time (e.g. earlier commits record
text files with CRLF line endings, but recent ones use LF line
endings). In such a repository, Git can convert the data
recorded in commits to a canonical form before performing a
merge to reduce unnecessary conflicts. For more information,
see section "Merging branches with differing checkin/checkout
attributes" in gitattributes[5].

merge.stat

Whether to print the diffstat between ORIG_HEAD and the merge result
at the end of the merge. True by default.

merge.tool

Controls which merge tool is used by git-mergetool[1].
The list below shows the valid built-in values.
Any other value is treated as a custom merge tool and requires
that a corresponding mergetool.<tool>.cmd variable is defined.

Controls the amount of output shown by the recursive merge
strategy. Level 0 outputs nothing except a final error
message if conflicts were detected. Level 1 outputs only
conflicts, 2 outputs conflicts and file changes. Level 5 and
above outputs debugging information. The default is level 2.
Can be overridden by the GIT_MERGE_VERBOSITY environment variable.

merge.<driver>.name

Defines a human-readable name for a custom low-level
merge driver. See gitattributes[5] for details.

merge.<driver>.driver

Defines the command that implements a custom low-level
merge driver. See gitattributes[5] for details.

merge.<driver>.recursive

Names a low-level merge driver to be used when
performing an internal merge between common ancestors.
See gitattributes[5] for details.

branch.<name>.mergeoptions

Sets default options for merging into branch <name>. The syntax and
supported options are the same as those of git merge, but option
values containing whitespace characters are currently not supported.